1. Field of the Invention
The present invention relates to signal processing systems and methods. In particular, the present invention relates to a method and system for generating ultra wideband signals.
2. Background Information
Applications that can benefit from very wide band signal sources, include foliage penetrating radars, remote material identification, and the like. These applications often require high RF transmit power as well a very wide band signal to increase stand off range and/or improve system signal to noise ratios. Generating a high power ultra wideband (UWB) signal is very difficult. In addition to the normal problems of creating and handling high RF fields, the available devices for high power amplification are very dispersive. The dispersive characteristic of a high power broadband amplifier causes the different spectral components to experience vast phase and amplitude variation as they pass through the amplifier. This results in distortion of the desired signals. While it is possible to xe2x80x98predistortxe2x80x99 the signal before amplification, this is often a difficult and delicate process that is not desirable.
Known devices generate the desired signal at low power levels, using some sort of a synthesizer or waveform generator, then amplifying it in a broadband power amplifier. The dispersion characteristics of the broadband power amplifier, (phase vs. frequency) often distort the signal unacceptably. Therefore, there is a need for a method and system that eliminates the need for broadband high power amplifiers and the dispersion such devices produce.
The present invention is directed to methods and systems for generating an ultra wideband signal. An exemplary method comprises: generating a first tone that has a frequency one half of a desired frequency of the ultra wideband signal, wherein the ultra wideband signal is a sine wave that inverts phase every cycle; generating a second tone that has a frequency three halves of the desired frequency; amplifying the first and second tones independently to generate an amplified first tone and an amplified second tone; and combining the amplified first and second tones to form the ultra wideband signal. Additionally, the method provides for generating and combining additional tones to the first and second tones, wherein the additional tones have frequencies of, for example, five halves and seven halves of the desired frequency, respectively.
An exemplary system for generating an ultra wideband signal comprises: an oscillator that generates a first tone that has a frequency one half of a desired frequency of an ultra wideband signal, wherein the ultra wideband signal is a sine wave that inverts phase every cycle; a means for generating a second tone that has a frequency three halves of the desired frequency; a first amplifier that amplifies the first tone and a second amplifier that amplifies the second tone to generate an amplified first tone and an amplified second tone; and a means for combining the amplified first and second tones to form the ultra wideband signal.